Roofing Contractors and Designers Responsibility
Roofing contractors are responsible for the installation of roofing systems. The responsibility for design and specifications of a roof falls to the designer of record. This includes, but is not limited to, determination of all design loads (structural and environmental), and compliance with all applicable codes.
The concept of design responsibility is addressed in Guidelines for a Successful Construction Project (2003) published by the Associated General Contractors of America, in collaboration with the American Subcontractors Association, and the Associated Specialty Contractors. According to the authors, “Long experience demonstrates that a clear division of responsibility between the architect, as designer, and the contractor, as builder, offers an effective way to achieve fast, safe, and economical construction results.”
The document states:
“All owners, architects and other design professionals are urged to uniformly accept responsibility for design related plans and specifications applying to construction projects. This design responsibility includes drafting complete specifications for inclusion in project bidding documents, initiating or approving all design-related additions, deletions and changes to project specifications and accepting ultimate responsibility for the safety and utility of all project design elements.”
“Contractors and subcontractors must not be held responsible for the adequacy of the performance or design criteria indicated by the contract documents.”
The introduction of the National Building Code Canada 2015 (NBCC 2015) has focused the attention of design professionals on wind uplift and the wind uplift resistance of commercial roof systems.
Some designers have responded positively to the code changes by issuing project specifications that provide the wind uplift loading for the specific project and that require the roofing contractor to install an assembly tested to the requirements of CSA A123.21 Standard test method for the dynamic wind uplift resistance of membrane-roofing systems that provides the necessary wind uplift resistance. This approach follows the requirements of the NBCC 2015. It is straight forward – responsibilities and requirements are clear.
Unfortunately, a significant number of designers are choosing to download all responsibility related to roof wind uplift to the roofing contractors. Some project specifications are being issued that include a catch all sentence requiring the roofing contractor to comply with code requirements – no specifics. Other specifications include wording that requires the roofing contractor to determine wind loads and to install a roof assembly that meets these loads. Still others take it a step further and require the roofing contractor to provide wind uplift calculations and roof shop drawings that are stamped by a professional engineer.
In accordance with these design principles, roofing contractors are cautioned to watch for project specifications that effectively download design responsibility to the roofing contractor.
When this type of specification is encountered, it is strongly recommended that the project specifier be requested to amend the specifications and remove the requirement for the roofing contractor to act as a designer. If an addendum to the project specification isn’t possible, the roofing contractor will need to decide whether to hire a qualified design professional and include these costs in their tender price; qualify their tender to avoid taking on design responsibility or decline to bid on the project.
The opinions expressed herein are those of the CRCA National Technical Committee. This Advisory Bulletin is circulated for the purpose of bringing roofing information to the attention of the reader. The data, commentary, opinions and conclusions, if any, are not intended to provide the reader with conclusive technical advice and the reader should not act only on the roofing information contained in this Advisory Bulletin without seeking specific professional, engineering or architectural advice. Neither the CRCA nor any of its officers, directors, members or employees assumes any responsibility for any of the roofing information contained herein or the consequences of any interpretation which the reader may take from such information.